Art of cracking hydrocarbons



1. W. COAST, la. ABT 0F CRACKING HYDRocAHoNs.

APPLICATION FILED SEPT. 27, 1917.

Patented Aug. 23, 1921.

m /ffff UNITED STATES PATENT orifice.

JOHN W. COAST, JR., OF TULSA, OKLAHGMA, ASSIGNOR T0 THE PROCESS CQMPANY, OF TULSA, OKLAHOMA, A CORPORATION OF MARYLAND.

To all'whom'z't 'may concern Be it known that I, JOHN W. CoAs'r, Jr., a citizen of the United States of America, a resident of Tulsa, in the county of Tulsa, State of Oklahoma, have invented certain new and useful Improvements in the Art of Cracking Hydrocarbons, of which the following is a full, clear, and exact desemption, reference being had to the accompanying drawing, forming a part of this speciiication.

This invention relates to improvements in the art of cracking hydrocarbons, and more particularly to a method of treating petro-- leum hydrocarbons to obtain a product known as gasolene, cracked gasolene and by other names designating an explosive oil suitable for use in internal combustion engines. Some of the objects of the invention are to avoid the danger, expense and loss of time usually due to the presence of cokeforming matter in cracking stills; to economize in the use of fuel, and to utilize the hot fluid discharged from a cracking coil as a heating medium for the liquid contents of a still. Another object is to maintain the apparatus in continuous operation for a considerable period of time, without removing the coke-forming matter.

In the preferred form of the invention a body of hydrocarbon oil is maintained in a vlarge cylindrical cracking still, and the hot Huid discharged from a cracking coil is utilized to heat said body of oil. The contents of the cracking coil are preferably subjected to a very hi h degree of heat and forced into the Vbody o oil in the cylindrical still, the vapor assing from said coil being permitted to bub le through said bodyof oil. The liquid contents of the cylindrical still are thus commingled with and heated by the hot fluid discharged from the coil. 'Ihe temperature of thisfluid is so high that the desired cracking takes place. in the still without transmitting the usual high degree of heat through the metal of the still. As a result, the transmission of heat to the body of oil is not greatl affected by the presence of coke on the sti l bottom, and the. danger usually due to overheatin a cylindrical still is almost] entirely el1minated.` Furthermore, the losses due to the transmission of heat through a body 0f coke are minimized for the coke on the still bottom does not in any way interfere with the transmission of heat from Specification of Letters Patent.

Patented Aug. 23, 1921.

Application filed. September 27, 1917. Serial No. 193,472.

the preheated fluid to the body of oil. This hot fluid also increases the efficiency of the apparatus by circulatin the liquid in the still.. By eliminating tie danger of overheating the cylindrical still, and at the same time subjecting the oil t0 the necessary high temperature, the apparatus can be operated continuously for a considerable period of time.

To fully appreciate a most important feature of this invention, it will be necessary to understand that some oils can be cracked more readily lthan others. High boiling point oils can be easily cracked to produce gasolene, but the saine is not true of lighter oils, such as distillates of the illuminating oil series. For example, high boiling point oils, such as gas oil and fuel oil,`can be very successfully cracked in a large cylindrical cracking still at a temperature of about 7 50J F. and a pressure of about 85 pounds per square inch, whereas lighter oils, such as distillates of the illuminating oil series, must be subjected to higher pressures and higher temperatures. In actual practice, I vhave found that it is economical and otherwise desirable to crack the high boiling point oils in a large fire heated cylindrical cracking still, and that lower boiling point-oils of the illuminating oil series can be very successfully cracked in a cracking coil maintained at a relatively high pressure and at a correspondingly high temperature. According to the present invention, high boiling point oils and-low boiling point oils are cracked simultaneously, and each body of oil is subjected to the conditions most favorable for the conversion of its constituents into cracked gasolene. The high boiling point oil, preferably gas oil or fuel oil, is cracked under ressure in an ordinary cylindrical still. he low boiling point oil, preferably a distillate of the illuminating oil series, is subjected to a higher pressure and to a higher temperature, and then discharged into the cylindrical cracking still. The different oils are thus subjected to most desirable conditions, and the fluid discharged from the hottest still is forced into the oil undergoing distillation at a lower temperature in the cylindrical still.

The drawing is a diagrammatical View of a cracking apparatus adapted for use in carrying out the new method.

To illustrate the invention I have shown a sol cracking apparatus comprisin a large hori- Zontal cylindrical cracking still 1 arranged above a heating chamber 2, a vapor pipe 3 leading from said still to an air cooled reflux condenser 4, a second reflux condenser 4 arranged to receive the vapor flowing from the condenser 4, and a vapor pipe 5 connecting said reflux condenser 4 to a water cooled condenser 6 from Which the product is recovered. A pressure regulating valve 7 preferably located in the vapor pipe 5, maybe regulated to maintain a predetermined pressure in the reflux condensers and still 1. In the reflux condensers, the fractions having relatively high boiling points are condensed and separated from the lighter fractions which pass to the main condenser 6. VThe high boiling point condensate formed in the reflux condensers, flows into a pipe 8 whereby it is conducted back to the still 1.

A perforated discharge pipe 9, submerged in the lower portion of the still 1, is connected by means of a pipe 10 to the dischar e end of a fire heated cracking coil 11, t e latter consisting of a coil of pipe arranged within a furnace or heating chamber 12.

The apparatus herein shown is particularly adapted for use in cracking distillates or residues resulting from the. distillation of petroleum. A body of hydrocarbon oil is maintained in the large cylindrical still 1, and this oil is maintained at a cracking temperature, partly by the heattransmitted from the fire in the heating chamber 2, and partly by streams of hot fluid discharged from the perforated pipe 9. A fresh charge of oil is conducted through a pipe 13 to a pump 14, which forces the oil through a pipe'15 and into the cracking coil 1l. Steam passlng from a pi-pe 16 is discharged into the pipe 15 where it commingles with the oil flowing into the coil. The mixture of steam and hydrocarbons is forced through the coil at a high velocity and discharged into the pipe 10 leading to the perforated pipe 9 at the bottom of the cylindrical still.

l It will be observed that the structure herein shown comprises a primary cracking apparatus including the cracklng coil 11, a secondary cracking apparatus including a large still'l, and a condenser 6 common to the primary and secondary cracking apparatus.

The oil introduced into the cracking coil may be a distillate of the illuminating oil series having a boiling point of about 500 F., and a gravity of about 42 B., and the body of oil introduced into the large cylindrical still 1 may be a fuel oil, or a gas oil having a gravit of about 32 B. and a boiling point o about 600 F. In other words, I preferably introduce a low boiling 'point distillate into the cranking coil and a high boiling point distillate into the cylindrical still l. A fresh charge of the high boiling point oil may be forced from a supply pipe 18 through a pump 19 and thence through a pipe 20 to the pipe 10 leading into the still 1. To successfully crack the low boiling point oil, itis necessary, or desirable, to use extremely high pressures and temperatures, and it would be dangerous and uneconomical to operate the large cylindrical still 1 under such pressures and temperatures. However, the small tubes forming the cracking coil 11 can withstand a much higher pressure and a much higher temperature than the large cylindrical still. It is, therefore, an advantage to maintain the contents of the cracking coil under a higher pressure and at a higher temperature than the cylindrical still. The difference in pressure can be obtained by adjusting a valve 21 in the pipe 10 leading from the cracking coil to the cylindrical still.

The contents of the cracking coil may, for example, be subjected to the pressure of about 150 pounds per square inch, and a temperature of about 900 F., While the contents of the cylindrical still 1 are maintained at a pressure of about 85 pounds per square inch and a temperature of about 750 F. It will, of course, beunderstood that thev invention is not in any way limited to the use ticular temperature, but it is important to observe that the low77 boilin pointl oil in the cracking coil is subjecte to a hi her pressure and to a higher temperature t an the ressure and temperature of the hi h boiling point oil in the large cylindrical still. The reasons for these differences in pressure and temperature have already been pointed out.

The vapor discharged from the cracking coil at a very high temperature bubbles through the body of oil in the cylindrical still, and serves as a very effective heating medium for the oil. By transmittin heat to vthe interior of the cylindrical still 1n this manner, a lower fire can be used under the cylindrical still, thus economizing in the use of fuel and avoiding the vdan er of overheating the bottom of the cylin rical still.

I claim 1. In the art of cracking high boiling point and low boiling point hydrocarbon oils, the method which com rises maintaining a body of the high boiling point oil in a. crackin still, forcing. the low boiling pointoil into a crackin coil, discharging the contents of the crac 'ng coil'into sai high boiling point oil in the still, maintaining the low boiling point oil under a relatively high pressure and at a relatively high temperature, and maintaining the high b011- ingv point oil under a lower pressure and at a ower temperature.

2. In the art of cracking high boiling of any specific pressure, nor to any par- Y point and low boiling point hydrocarbon oils, the method which comprises maintaining a body of the high boiling point oil in a large cylindrical cracking still, forcing the low boiling point oil into a cracking coil, subjecting the high boiling point oil in the cylindrical still to a cracking telnperature and a cracking pressure, subjecting the low boiling point oil in the cracking coil to a pressure and temperature higher than that of the cylindrical still, and at the same time discharging the cracked product from the cracking coil and into the oil in said cylindrical still.

3. In the art of cracking high boiling point and low boiling point hydrocarbon oils, the method which comprises maintaining a body of gas oil in a cracking still, forcing a distillate of the illuminating oil series mto. a cracking coil, discharging the contents of the cracking coil into the oil in said still, maintaining the distillate of the illuminating oil series under a relatively high pressure and at a relatively high temperature, and maintaining the gas oil under a lower pressure and at a lower temperature. K

4. In the art of cracking` high boiling point and low boiling point hydrocarbon oils, the method which comprises maintaining a body of the high boiling point oil in a large cylindrical cracking still, forcing a low boiling point oil of the illuminating series into a cracking coil, subjecting the high boiling point oil in the cylindrical still to a cracking temperature and a cracking pressure greater than 50 pounds per square inch, subjectin the low boiling point oil of the illuminatlng series in the cracking coil to a pressure and temperature higher than that of the oil in the cylindrical still, and at the same time discharging the cracked product from the cracking coil and into the oil in said cylindrical still.

5. In the art of cracking high boiling point and low boiling point hydrocarbon oils, the method which comprises maintain-4 ing a body of the high boiling point oil in a cracking still, forcing the low boiling point oil into a cracking coil, commingling steam with the low boiling point oil in the cracking coil, discharging the contents of the cracking coil into the oil in said still, maintaining the steam and low boiling point oil under a relatively high pressure and at a relatively hi h temperature, and maintaining the hig boiling point oil under a lower pressure and at a lower temperature sufficient for cracking.

In testimony that I claim the foregoing I hereunto aHx my si ature.

JOH W. COAST, JR. 

